 working as an assistant professor in Department of Mechanical Engineering, Valchin Institute of Technology, Solapur. So, today in the third session, we will see psychometric properties and numericals. Learning outcomes. At the end of this session, students will be able to derive specific enthalpy and evaluate psychometric properties. Now, in this session, we will see the specific humidity of moisture. Specific humidity of moisture is equal to humidity of dry air plus humidity of water vapor. If I consider the humidity per mass of air, then on both sides, I will divide it by M A, which is equal to M A into specific enthalpy of air by M A plus M V into H V by M A. So, specific enthalpy of moisture is equal to a specific enthalpy of dry air plus this ratio is specific humidity into H V. Now, this is the equation number first. As we know, specific humidity of dry air as the air is in the gaseous phase, we can consider C P A means specific humidity, specific heat of air into driable temperature. Now, this driable temperature is nothing but small t, which is the same of air and water vapor. This is the equation number second. Now, to find the enthalpy of vapor, we have to refer the Moulier chart. So, on the Moulier chart, if we refer the Moulier chart, it is found that up to 50 degrees Celsius, the isenthalpic lines and isothermal lines are coinciding. So, if I draw here the isothermal line, then corresponding to isothermal, the isenthalpic lines are also coinciding on the same. So, what I can do? I can consider the reference temperature for the water vapor as 0 degree Celsius and the enthalpy of water vapor, instead of taking it as a dry air, that is suppose capital A, superheated B or state C. I can derive the general relation for the water vapor. So, H V is equal to H F G. This is the latent heat at 0 degree Celsius plus C p V specific humidity of superheated vapor into driable temperature minus 0. So, it becomes H F G at 0 degree Celsius plus C p V into d B T driable temperature. If we refer the steam table, then at 0 degree Celsius, we will get the value of latent heat of vaporization as 2501 plus the C p V is 1.88 into T. This is the equation number 3. Then, I should substitute the values of H A and H V in equation number first. So, enthalpy of moisture will be equal to C p A T plus omega into bracket 2501 plus 1.88 T as C p A is 1.005 T plus specific humidity into bracket 2501 plus 1.88 T. So, this is the derivation of specific enthalpy of moisture. Next is numerical on moisture. There are two types of the numericals. In first category, they will be giving driable temperature and wet ball temperature. By using the psychrometer, we can obtain driable temperature and wet ball temperature. And if we refer this T as plot, then corresponding to driable temperature from steam table, we will get P S. And from wet ball temperature by referring this T as plot, we will be getting P V dash. Here, we require to refer the carriers equation. This is the first type of the numerical. In second type, we will be knowing along with the driable temperature either relative humidity or specific humidity or degree of saturation. So, by equations, we can find out the other psychrometric properties. Now, if I cool the air at P V pressure, then from steam table, I may get the dew point temperature. So, this is the third method from which I can obtain the dew point temperature of that air, moist air. Next is the psychrometric processes. This is the psychrometric chart. I will consider 25 degree Celsius as driable temperature and 50 percent RH. The intersection of these two properties will be the reference point. So, if I will heat the moist air without changing the specific volume, sorry, specific humidity, this process is known as sensible heating process. 1 to 2 is sensible heating process. If I cool it means, without changing omega, if I decrease its driable temperature, the process 1 to 3 will be called sensible cooling process. If I start adding the water vapor because omega is equal to m v by m a, if I will start adding the mass of water vapor in that moist air, then there will be increase in the omega. 1 to 4 will be known as humidification process. The reverse, if I remove the water vapor from that moist air, then 1 to 5 will be known as dehumidification process. Now, I can get the mixed processes also. That is, process 1 to 6 will be heating with humidification and reverse cooling with dehumidification 1 to 7. Then 1 to 8 will be cooling with humidification and 1 to 9 will be heating with dehumidification. So, these are the different psychometric processes. Thank you.